The Bit-Exact
Physics Engine

SunaEngine is an open-source particle physics engine that guarantees bit-identical simulation output — every time, everywhere, on any WebGPU-capable device.

WebGPU 256-bit State Hash Integer-Only Math Zero Floating Point GPL-3.0 Licensed

Demo 1 — Deterministic Twin

Two identical water columns, seeded from the same bytes. Watch them fall and settle — their 256-bit state hash stays byte-for-byte identical through every frame.

Hash: Hash:
Frame: 0   Particles: 0

Demo 2 — Push & Rewind

Drag through the water to push it around. Use the slider to scrub backward and forward through the simulation. Every frame is deterministic — the same inputs always produce the exact same result.

Frame: 0 Hash: Snapshots: 0
Frame 0/0

Why SunaEngine?

Most physics engines use floating-point math that varies between devices. SunaEngine doesn't.

🔒

Bit-Exact Determinism

Integer-only fixed-point arithmetic eliminates floating-point variance. Same input → same 256-bit hash, guaranteed, on any GPU.

WebGPU Native

Runs compute shaders directly on the GPU for maximum throughput. Thousands of particles at real-time frame rates.

📐

Position-Based Dynamics

The PBF solver handles density constraints, viscosity, cohesion, and surface tension — all in exact integer math.

🪶

Minimal & Focused

No temperature, no reactions, no material presets. Just the pure solver core, ready to build on.

🔄

Replay & Rewind

Record input sequences and replay them deterministically. Perfect for networked games, replays, and verification.

🌐

Cross-Platform

Runs in any browser with WebGPU support. Chrome, Edge, Firefox Nightly — same bytes, same hash, everywhere.

Engineering Specs

Q16.16
Fixed-Point Format
i32
Arithmetic Type
256-bit
State Hash (Murmur3)
RNE
Rounding (Half-to-Even)
32 B
Per-Particle State
2.5 wu
Kernel Radius